Along with continuous development of a network technology and continuous popularization of various types of terminal equipment, social networks have become more and more important to lives of people, and have even become a part of the lives of the people. In these virtual network spaces, users may manage own friend circles in real lives, so that the social networks become windows for people to acquire information, show themselves and implement marketing promotion. Therefore, how to rapidly increase the number of users to expand friend circles of the users in a social network becomes an important research subject of this field.